RESUMEN

Evaluation at all levels is a fundamental function at World Health Organization (WHO). Evaluation of public health surveillance systems is essential to ensure that problems of public health importance are monitored efficiently and effectively. The WHO's Vitamin and Mineral Nutrition Information System (VMNIS) was evaluated from the perspective of public health surveillance and informatics. Steps included: engaging the stakeholders of the evaluation; describing the surveillance system; focusing the evaluation design; gathering credible evidence regarding system performance; justifying and stating conclusions and recommendations, and sharing lessons learned from the evaluation. Following this assessment, WHO has begun major efforts to upgrade and expand the VMNIS and now the database is more flexible and efficient. The database evaluation summarized in this paper provides a good example of how public health evaluation frameworks can lead to improved surveillance and enhanced information systems, thus making progress toward the ultimate goal of improving public health.

La evaluación en todos los niveles es una función fundamental en la Organización Mundial de la Salud (OMS). La evaluación de los sistemas de vigilancia epidemiológica es esencial para asegurar que los problemas de importancia para la salud pública sean monitorizados de manera eficiente y efectiva. El Sistema de Información Nutricional sobre Vitaminas y Minerales (VMNIS, por sus siglas en inglés) se evaluó desde la perspectiva de sistema de vigilancia e informática en salud pública. Los pasos incluyeron: el involucramiento de las partes interesadas en la evaluación, la descripción del sistema de vigilancia, el enfoque del diseño para la evaluación, la recopilación de pruebas fiables sobre el rendimiento del sistema, la justificación y desarrollo de conclusiones y recomendaciones, y la diseminación de las lecciones aprendidas de la evaluación. Después de este proceso, la OMS inició importantes esfuerzos para mejorar y ampliar el Sistema de Información Nutricional sobre Vitaminas y Minerales para lograr una base de datos más flexible y eficiente. Este artículo resume la evaluación de esta base de datos para documentar un buen ejemplo de cómo los marcos de evaluación en salud pública pueden llevar a mejorar la información en los sistemas de vigilancia contribuyendo de esta manera al objetivo final de mejorar la salud pública.

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RESUMEN

Evaluation of public health surveillance systems is essential to ensure that problems of public health importance are monitored efficiently and effectively. The WHO's Vitamin and Mineral Nutrition Information System (VMNIS) was evaluated from the perspective of public health surveillance and informatics. Steps included: engaging the stakeholders of the evaluation; describing the surveillance system; focusing the evaluation design; gathering credible evidence regarding system performance; justifying and stating conclusions and recommendations, and sharing lessons learned from the evaluation. Following this assessment, WHO has begun major efforts to upgrade and expand the VMNIS and now the database is more flexible and efficient. The database evaluation summarized in this paper provides a good example of how public health evaluation frameworks can lead to improved surveillance and enhanced information systems, thus making progress toward the ultimate goal of improving public health.

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BACKGROUND: Studies conducted in Guatemala, Mexico, and Venezuela have found high prevalences of low plasma cobalamin (vitamin B-12) concentrations in infants and children. It is not known whether these low cobalamin concentrations are accompanied by altered metabolic functions. OBJECTIVE: We sought to assess the prevalence of cobalamin deficiency in Guatemalan children by using sensitive and specific markers of deficiency. DESIGN: Children (n = 553) were screened for low plasma cobalamin. Those with low plasma cobalamin (< 162 pmol/L) were matched by age, grade, and sex to those with marginal (162-221 pmol/L) and adequate (> 221 pmol/L) concentrations. In this matched subset (n = 180), additional biochemical indicators of cobalamin deficiency were measured. RESULTS: Of the 553 children screened, 11% had low plasma cobalamin and an additional 22% had marginal concentrations. The prevalences of elevated serum methylmalonic acid (MMA), plasma homocysteine, or both were significantly higher in children with low and marginal plasma cobalamin than in children with adequate plasma cobalamin. Mean serum MMA was high in all groups compared with values reported in other populations. Mean plasma holotranscobalamin II concentrations were significantly lower in children with low rather than marginal or adequate plasma cobalamin. However, holotranscobalamin II was a less sensitive indicator of cobalamin depletion than was MMA. CONCLUSION: Biochemical markers of cobalamin deficiency confirmed that the cobalamin status of children with low and marginal plasma cobalamin is inadequate to support normal metabolic function.

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OBJECTIVES: The authors investigated whether low vitamin B12 intake, impaired gastric function, infection, and bacterial overgrowth were risk factors for the high prevalence of cobalamin deficiency observed in Guatemalan children. METHODS: The plasma cobalamin concentration of 556 school children was measured and classified as low, marginal, or adequate. In 60 children from each of these three groups, concentrations of serum methylmalonic acid (MMA), plasma homocysteine, and plasma holotranscobalamin II were measured, and usual dietary B12 intake was estimated. Serum gastrin and pepsinogen I concentrations were measured, and and bacterial overgrowth were diagnosed using C-urea and C-xylose breath tests, respectively. RESULTS: infection was present in 83% (144 of 174) of children, and bacterial overgrowth was found in 25% (28 of 113). Children with infection had higher serum gastrin and pepsinogen I. There were no significant differences among the plasma cobalamin groups in the prevalence of infection, bacterial overgrowth, serum gastrin, or pepsinogen I concentrations. However, there was a significant positive correlation between serum MMA and gastrin concentrations. The average daily consumption of dietary B12 was 5.5 +/- 5.2 microg/day, but intakes for 23% of children were <1.8 micro g/day. B12 intake from fortified snacks added an additional 0.3 +/- 0.2 microg/day. B12 intake was not significantly different among the plasma cobalamin groups, but it was significantly correlated with plasma cobalamin. CONCLUSIONS: The specific cause of cobalamin deficiency in this population remains unclear, but these results suggest that low dietary B12 intake is a risk factor and alterations in gastric secretions may also play a role.

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